Ultrasound probes include one-dimensional (1D) or two-dimensional (2D) transducer arrays. An example of one dimensional (1D) transducer 102 is illustrated in FIG. 1 and includes a plurality of generally rectangular shaped elements 104, such as elements 1041, 1042, 1043, 1044, . . . , 104N (where N is an integer equal to or greater than one), arranged consecutively along a long or longitudinal axis 105 of the one dimensional transducer 102. Each of the elements 104 has a physical width (W) 106 and a height (H) 108 and is separated from a neighboring element 104 by a spacing (S) 110 such as a kerf resulting from a dice-and-fill or other element forming approach.
The transducer array 102 has a pitch (P) 112, which, in this example, is defined by a center-to-center distance of neighboring elements 104 (e.g., 1041 and 1042) and is equal to a summation of half of a width of one of the neighboring elements, half of a width of the other neighboring element, and the spacing 110 between the neighboring elements (i.e., P=½*W+½*W+S). As such, in this example, the width 106 is always less than the pitch 112. The transducer array 102 has a length (L) 114, which is dependent on the number of elements 104, the width 106 and the spacing 110. Note that the illustrated geometry (e.g., width 106, height 108, spacing 110, pitch 112, and length 114) is for explanatory purposes and is not limiting.
With further reference to FIG. 1, and with reference to FIG. 2, an example radiation pattern 202 of the transducer array 102 in connection with an element factor 204 (which defines the imaging region or field of view of an element) for one of the elements 104 is shown as a function of the length 114 of the transducer 102 at a given distance away from the array 102 and focus. The radiation pattern 202 includes a main lobe 206, side lobes 208, and gating lobes 210. As shown, locations of zero crossings 212 of the element factor 204, with respect to the main lobe 206, are inversely proportional to the width 106 (e.g., ˜1/W), and locations of the gating lobes 210, with respect to the main lobe 206, are inversely proportional to the pitch 112 (e.g., ˜1/P).
With this configuration, the gating lobes 210 are located between the zero crossings 212 and the main lobe 206, and inside of the element factor 204 and hence in the field of view or imaging region of the element 104. Unfortunately, such grating lobes introduce artifacts into the images generated with the data acquired by the transducer 102. Examples of such artifacts include dark shadows inside of bright areas, shadows behind darker areas, ghost flow at the edges of vessel or in place of tissue where there are no vessels, and/or other artifacts.
One approach for reducing such artifacts is to reduce the pitch to avoid large grating lobes. This can be achieved through utilizing narrower width elements 104. Unfortunately, narrower elements have poorer signal-to-noise characteristics and a greater impendence mismatch with the cables interfacing the elements. Furthermore, a greater number of narrower elements, relative to wider elements, are needed for a given array aperture or length, and increasing the number of elements tends to increase the cost of the transducer array.